Focus detection device, imaging device, and interchangeable lens

ABSTRACT

A focus detection device includes: an imaging unit having a first and second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection, and a third pixel which receives light transmitted through the optical system and outputs signal used for image generation; an input unit to which information regarding the optical system is input; a selection unit that selects one of the first and second pixel based on the information to the input unit; a readout unit that reads out the signal from one of the first and second pixel based on a selection result at a timing different from reading out the signal from the third pixel to be read out; and a focus detection unit that performs the focus detection based on at least one of the signals of the first and second pixel read out by the readout unit.

TECHNICAL FIELD

The present invention relates to a focus detection device, an imagingdevice, and an interchangeable lens.

BACKGROUND ART

An image sensor that reads out a signal for focus detection and a signalfor image generation is known (for example, Patent Literature 1: PTL1).In such an image sensor, it is desired to increase the speed of signalreading.

CITATION LIST Patent Literature

PTL 1: Japanese Laid-Open Patent Publication No. 2017-34606

SUMMARY OF INVENTION

According to the 1st aspect of the present invention, a focus detectiondevice comprises: an imaging unit having a first pixel and a secondpixel each of which receives light transmitted through an optical systemand outputs signal used for focus detection, and a third pixel whichreceives light transmitted through the optical system and outputs signalused for image generation; an input unit to which information regardingthe optical system is input; a selection unit that selects at least oneof the first pixel and the second pixel based on the information inputto the input unit; a readout unit that reads out the signal from atleast one of the first pixel and the second pixel based on a selectionresult of the selection unit at a timing different from a timing ofreading out the signal from the third pixel to be read out; and a focusdetection unit that performs the focus detection based on at least oneof the signals of the first pixel and the second pixel read out by thereadout unit.

According to the 2nd aspect of the present invention, an imaging devicecomprises: the focus detection device according to the 1st aspect, and ageneration unit that generates image data based on signals output fromat least one of the first pixel, the second pixel, and the third pixel.

According to the 3rd aspect of the present invention, an interchangeablelens comprises: a detachable portion that enables to attach and detachto the focus detection device according to the 1st aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration example of an imaging deviceaccording to the first embodiment.

FIG. 2 is a diagram showing a focus detection area of an imaging surfaceof the imaging device according to the first embodiment.

FIG. 3 is a diagram showing an arrangement example of pixels in thefocus detection area of the imaging device according to the firstembodiment.

FIG. 4 is a diagram showing a s configuration example of pixels in theimaging device according to the first embodiment.

FIG. 5 is a cross-sectional view showing three types of AF pixel pairsto be arranged at the central region of the imaging device according tothe first embodiment.

FIG. 6 is a cross-sectional view showing three types of AF pixel pairsto be arranged at a region corresponding to a predetermined image heightin the imaging device according to the first embodiment.

FIG. 7 is a cross-sectional view showing three types of AF pixel pairsto be arranged at a region corresponding to a predetermined image heightin the imaging device according to the first embodiment.

FIG. 8 is a diagram showing the relationship between the reference exitpupil and the image height in the imaging device according to the firstembodiment.

FIG. 9 shows various optical characteristics of an interchangeable lenswhose exit pupil distance changes according to the image height, in theimaging device according to the first embodiment.

FIG. 10 is a diagram showing the relationship between the image heightand the exit pupil in the imaging device according to the firstembodiment.

FIG. 11 is a table showing a constant term and coefficients of afunction that approximates representative optical characteristic curvein each focus position zone in the imaging device according to the firstembodiment.

FIG. 12 is a table showing a constant term and coefficients of afunction that approximates representative optical characteristic curvein each zone in the imaging device according to the first embodiment.

FIG. 13 is a diagram showing, in the imaging device according to thefirst embodiment, a threshold value of an exit pupil distance, first tothird exit pupil distance ranges, and an optical characteristic curve.

FIG. 14 is a diagram showing a circuit configuration of the pixel of animage sensor according to the first embodiment.

FIG. 15 is a diagram showing a configuration of part of the image sensoraccording to the first embodiment.

FIG. 16 is a diagram showing a configuration sample of an AF pixel of animage sensor according to a variation.

FIG. 17 is a diagram showing a configuration sample of an AF pixel of animage sensor according to a variation.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a diagram showing a configuration example of an electroniccamera 1 (hereinafter, referred to as a camera 1) which is an example ofan imaging device according to the first embodiment. The camera 1 isconfigured with a camera body 2 and an interchangeable lens 3. Since thecamera 1 is configured with the camera body 2 and the interchangeablelens 3, it is sometimes called a camera system.

The camera body 2 is provided with a body-side mount unit 201 to whichthe interchangeable lens 3 is to be attached. The interchangeable lens 3is provided with a lens-side mount unit 301 that is to be attached tothe camera body 2. The lens-side mount unit 301 and the body-side mountunit 201 are provided with a lens-side connection portion 302 and abody-side connection portion 202, respectively. The lens-side connectionportion 302 and the body-side connection portion 202 are each providedwith a plurality of terminals such as a terminal for a clock signal, aterminal for a data signal, and a terminal for supplying power. Theinterchangeable lens 3 is to be detachably attached to the camera body 2by the lens-side mount unit 301 and the body-side mount unit 201.

Upon being attached the interchangeable lens 3 to the camera body 2, theterminal provided on the body-side connection portion 202 and theterminal provided on the lens-side connection portion 302 areelectrically connected. Thereby, it becomes to be possible to supplypower from the camera body 2 to the interchangeable lens 3 or tocommunicate between the camera body 2 and the interchangeable lens 3.

The interchangeable lens 3 includes a photographing optical system(imaging optical system) 31, a lens control unit 32, and a lens memory33. The photographing optical system 31 includes, a plurality of lensesincluding a zoom lens (variable magnification lens) 31 a for changingthe focal length and a focusing lens (focus adjustment lens) 31 b, andan aperture 31 c, and forms a subject image on the imaging surface 22 aof the image sensor 22. Although the zoom lens 31 a and the focusinglens 31 b are schematically shown in FIG. 1 , a common photographingoptical system is generally configured with a lot of optical elements.

Further, as will be described later, the photographing optical system 31of the interchangeable lens 3 has an optical characteristic that theposition of the exit pupil thereof, that is, the exit pupil distancechanges depending on the image height. In other words, the exit pupildistance of the photographing optical system 31 changes depending on theposition on the imaging surface 22 a, that is, the distance from theoptical axis OA1 of the photographing optical system 31 on the imagingsurface 22 a. The optical axis OA1 of the photographing optical system31 intersects the imaging surface 22 a at the center position of theimaging surface 22 a. Here, the exit pupil distance is the distancebetween the exit pupil of the photographing optical system 31 and theimage plane of the image by the photographing optical system 31. It isto be noted, the imaging surface 22 a of the image sensor 22 is, forexample, a surface on which a photoelectric conversion unit describedlater is arranged or a surface on which a microlenses are arranged.

Moreover, the photographing optical system 31 differs depending on thetype of the interchangeable lens 3 to be mounted on the body-side mountunit 201. Therefore, the exit pupil distance of the photographingoptical system 31 differs depending on the type of the interchangeablelens 3. Further, the optical characteristics in which the exit pupildistance changes depending on the image height, also differ depending onthe type of the interchangeable lens 3.

The lens control unit 32 is configured with a processor such as a CPU,FPGA, and ASIC, and a memory such as ROM and RAM, and controls each partof the interchangeable lens 3 based on a control program. The lenscontrol unit 32 controls the position of the zoom lens 31 a, theposition of the focusing lens 31 b, and the drive of the aperture 31 cbased on the signal output from a body control unit 210 of the camerabody 2. Upon being input a signal indicating moving direction, movementamount or the like of the focusing lens 31 b from the body control unit210, the lens control unit 32 moves the focusing lens 31 b forward orbackward in the optical axis OA1 direction based on the signal, toadjust the focal position of the photographing optical system 31.Further, the lens control unit 32 controls the position of the zoom lens31 a and/or the aperture diameter of the aperture 31 c based on thesignal output from the body control unit 210 of the camera body 2.

The lens memory 33 is configured with, for example, a non-volatilestorage medium or the like. Information related to the interchangeablelens 3 is stored (recorded) as lens information in the lens memory 33.The lens information includes data on the optical characteristics (theexit pupil distance and/or an F number) of the photographing opticalsystem 31, data on the infinity position and the closest position of thefocusing lens 31 b, and data on the shortest focal length and thelongest focal length of the interchangeable lens 3. It is to be notedthat the lens information differs depending on the type of theinterchangeable lens 3. The lens information may be stored in theinternal memory of the lens control unit 32. Further, the lensinformation may be stored in the body memory 23 in the camera body 2described later. In this case, the body memory 23 stores the lensinformation of the plurality of types of interchangeable lenses 3.

In the present embodiment, the lens information includes informationregarding the exit pupil distance of the photographing optical system31. Although regarding the information with respect to the exit pupildistance will be described later, it includes the information indicatingthe exit pupil distance (Co) at the position where the imaging surface22 a and the optical axis OA1 intersect (the position where the imageheight is zero) and the information on coefficients (h4, h2) of thecalculation formula showing the relationship between the exit pupildistance and the image height. The writing of data to the lens memory 33and the reading of data from the lens memory 33 are controlled by thelens control unit 32. Upon being attached the interchangeable lens 3 tothe camera body 2, the lens control unit 32 transmits the lensinformation to the body control unit 210 via the terminals of thelens-side connection portion 302 and the body-side connection portion202. Further, the lens control unit 32 transmits position information(focal length information) of the zoom lens 31 a being controlled,position information of the focusing lens 31 b being controlled,information of the F number of the aperture 31 c being controlled, andthe like to the body control unit 210.

In the present embodiment, the lens control unit 32 functions as anoutput unit that transmits information regarding the exit pupil distanceof the photographing optical system 31 to the camera body 2. The bodycontrol unit 210 functions as an input unit being input information,from the interchangeable lens 3, regarding the exit pupil distance ofthe photographing optical system 31.

The lens control unit 32 performs bidirectional communication betweenthe camera body 2 and the interchangeable lens 3 via the terminals ofthe lens-side connection portion 302 and the body-side connectionportion 202. Upon being input a signal requesting transmission ofinformation (h4, h2, Co) regarding the exit pupil distance from thecamera body 2, the lens control unit 32 transmits the informationregarding the exit pupil distance to the camera body 2. It is to benoted that the information regarding the exit pupil distance differsdepending on the type of the interchangeable lens 3. Further, the lenscontrol unit 32 may transmit information regarding the exit pupildistance to the camera body 2 each time the image sensor 22 performs animage capturing. The lens control unit 32 may transmit informationregarding the exit pupil distance to the camera body 2 in a case wherethe zoom lens 31 a moves and the focal length of the photographingoptical system 31 changes. The lens control unit 32 may transmit theinformation on the focal length of the photographing optical system 31and the information on the exit pupil distance to the camera body 2 byone time bidirectional communication.

Next, the configuration of the camera body 2 will be described. Thecamera body 2 is provided with the image sensor 22, the body memory 23,a display unit 24, an operation unit 25, and the body control unit 210.The image sensor 22 is a CMOS image sensor, a CCD image sensor or thelike. The image sensor 22 performs an image capturing of a subject imageformed by the photographing optical system 31. In the image sensor 22, aplurality of pixels each having a photoelectric conversion unit arearranged in two-dimensional manner (row direction and column direction).The photoelectric conversion unit is configured with a photodiode (PD).The image sensor 22 performs photoelectric conversion of the receivedlight by the photoelectric conversion unit to generate a signal, andoutputs the generated signal to the body control unit 210.

As will be described later, the image sensor 22 has an imaging pixelthat outputs a signal used for image generation and an AF pixel (a focusdetection pixel) that outputs a signal used for focus detection. Theimaging pixel includes a pixel (hereinafter, referred to as an R pixel)having a filter of a spectral characteristic that spectrally dispersesthe light having the first wavelength region (red (R) light) from theincident light, a pixel (hereinafter, referred to as a G pixel) having afilter of a spectral characteristic that spectrally disperses the lighthaving the second wavelength region (green (G) light) from the incidentlight, and a pixel (hereinafter, referred to as a B pixel) having afilter of a spectral characteristic that spectrally disperses the lighthaving the third wavelength region (blue (B) light) from the incidentlight. The R pixel, the G pixel, and the B pixel are arranged accordingto the Bayer arrangement. The AF pixels are arranged by replacing a partof the imaging pixels and are dispersedly arranged on substantially theentire surface of the imaging surface 22 a of the image sensor 22. It isto be noted, in the following description, in a case the term “pixel” issimply used, it means either one or both of the imaging pixel and the AFpixel.

The body memory 23 is configured with, for example, a non-volatilestorage medium or the like. In the body memory 23, an image data, acontrol program, and the like are recorded. The writing of data to thebody memory 23 and the reading of data from the body memory 23 arecontrolled by the body control unit 210. The display unit 24 displays animage based on image data, an image showing a focus detection area (anAF area) such as an AF frame, information on photographing such as ashutter speed and the F number, a menu screen, and the like. Theoperation unit 25 includes various setting switches such as a releasebutton, a power switch, and a switch for switching various modes, andoutputs a signal corresponding to each operation to the body controlunit 210. Further, the operation unit 25 is a setting unit capable ofsetting an arbitrary focus detection area among a plurality of focusdetection areas, and a user can select the arbitrary focus detectionarea by operating the operation unit 25.

The body control unit 210 is configured with a processor such as a CPU,FPGA, and ASIC, and a memory such as ROM and RAM, and controls each partof the camera 1 based on a control program. The body control unit 210includes an area setting unit 211, a distance calculation unit 212, apixel selection unit 213, a readout unit 214, a focus detection unit215, and an image data generation unit 216.

The area setting unit 211 sets (selects) at least one focus detectionarea 100 among the plurality of focus detection areas 100 provided onthe imaging surface 22 a of the image sensor 22 shown in FIG. 2(a). Theplurality of AF frames displayed on the display unit 24 correspond tothe plurality of focus detection areas 100 provided on the image sensor22, respectively. The area setting unit 211 sets, among the plurality ofAF frames displayed on the display unit 24, the focus detection area 100corresponding to the AF frame selected by the user by operating theoperation unit 25, or the focus detection area 100 which is selected bythe camera 1 in automatically, as the area in which the focus detectionis performed. As will be described later, the focus detection unit 215detects the deviation amount (defocus amount) between the image by thephotographing optical system 31 and the imaging surface 22 a using asignal output from the AF pixel in the focus detection area 100 set bythe area setting unit 211.

As shown schematically in FIG. 2(b), in the focus detection area 100, inaddition to the imaging pixels, a plurality types of pair of the AFpixels (the AF pixel pairs) are arranged. In the present embodiment, afirst AF pixel pair, a second AF pixel pair, and a third AF pixel pairare arranged. The first AF pixel pair, the second AF pixel pair, and thethird AF pixel pair are arranged for accurately detecting the defocusamount at the exit pupil distance that differs depending on the imageheight or the type of interchangeable lens. One of the AF pixel amongthe AF pixel pair outputs a first signal Sig1, and the other of the AFpixel among the AF pixel pair outputs a second signal Sig2. The first AFpixel pair, the second AF pixel pair, and the third AF pixel pair willbe described later.

As shown in FIG. 2(a), the plurality of focus detection areas 100 arearranged in two-dimensional directions (row direction and columndirection), and the image height differs depending on arranged position.The small region 110 a (see FIG. 2(b)) in the focus detection area 100 aat the center part of the imaging surface 22 a is located on the opticalaxis OA1 of the photographing optical system 31, and the image height Hhere is substantially zero. As the focus detection area 100 being awayfrom the center (optical axis OA1 of the photographing optical system31) of the imaging surface 22 a, the image height H thereat increases.In other words, as the distance from the center of the imaging surface22 a to the focus detection area 100 increases, the image height Hthereat increases. Therefore, in the row where the focus detection area100 a exists, the focus detection areas 100 farthest from the opticalaxis OA1 of the photographing optical system 31 (the image height H isthe highest) are a focus detection areas 100 b and 100 c located at theleft end (the end in the −X direction) and the right end (the end in the+X direction). The focus detection areas 100 at which the image height His highest in the image sensor 22 are four focus detection areas 100 atthe corners of the imaging surface 22 a.

Since the focus detection area 100 has a predetermined area, the imageheight differs for each AF pixel depending on the position in the focusdetection area 100. That is, within the focus detection area 100, theimage height at the central small region 110 a (see FIG. 2(b)) isdifferent from the image heights at the small regions 110 b and 110 clocated at the left end (end in the −X direction) and the right end (endin the +X direction) respectively (see FIG. 2(b)). However, in thepresent embodiment, the value of the image height H at the centerposition of one focus detection area 100 is used as the valuerepresenting the image height of the entire focus detection area 100.The image height of the focus detection area 100 a in the center part ofthe imaging surface 22 a is zero, and the image heights of the focusdetection areas 100 b and 100 c are predetermined image heights H.

The distance calculation unit 212 calculates the exit pupil distance ofthe photographing optical system 31 at the image height H. The distancecalculation unit 212 calculates the exit pupil distance Po (H) of thephotographing optical system 31 at the image height H of the focusdetection area 100 set by the area setting unit 211 by the followingformula (1).Po(H)=h4×H ⁴ +h2×H ² +Co  (1)

Formula (1) is a calculation formula with the image height H as avariable, the parameter (h4) is the coefficient of the fourth-order termof the variable H, the parameter (h2) is the coefficient of thesecond-order term of the variable H, and the constant term Co is theexit pupil distance at the position where the image height is zero (theposition of the optical axis OA1 on the imaging surface 22 a). Theparameters (h4), (h2), and the constant term Co are information on theexit pupil distances corresponding to different image heights, and arevalues determined by the optical characteristics of the photographingoptical system 31. Information indicating the parameters (h4), (h2) andthe constant term Co is transmitted from the interchangeable lens 3 tothe camera body 2 as lens information. It is to be noted, thecalculation formula (1) is stored in the internal memory of the bodycontrol unit 210.

Based on the image height H of the focus detection area 100 set by thearea setting unit 211, the lens information (h4, h2, Co), and thecalculation formula (1), the distance calculation unit 212 calculatesthe exit pupil distance Po (H) for the image height H of the focusdetection area 100 having been set. It is to be noted that thecalculation formula (1) may be stored in the internal memory of the lenscontrol unit 32. The lens control unit 32 may transmit the calculationformula (1) to the camera body 2 as lens information together with theparameters (h4), (h2) and the constant term Co.

The pixel selection unit 213 selects at least one type of the AF pixelpair among a plurality of types of the AF pixel pairs provided in theimage sensor 22. In the present embodiment, the pixel selection unit 213selects any one type of three types of the AF pixel pairs (the first tothird AF pixel pairs) arranged in the focus detection area 100 set bythe area setting unit 211. As will be described later, the pixelselection unit 213 selects the AF pixel pair suitable for the exit pupildistance Po (H) calculated by the distance calculation unit 212 fromamong three types of the AF pixel pairs. In a case that a plurality offocus detection areas 100 are set by the area setting unit 211, thepixel selection unit 213 selects the same type of the AF pixel pair ineach selected focus detection area 100.

The readout unit 214 reads out a signal from the image sensor 22. In acase displaying a through image (live view image) of the subject on thedisplay unit 24 and/or in a case shooting a moving image, the readoutunit 214 reads out a signal used for image generation and/or a signalused for focus detection from the image sensor 22 at a predeterminedcycle. The readout unit 214 sequentially selects the pixels of the imagesensor 22 in row units and reads out the signal from the selected pixelrow, that is, by a so-called rolling shutter method.

The readout unit 214 can perform to read out in a first readout mode andin a second readout mode. In the first readout mode, the readout unit214 sequentially selects a row of pixels (hereinafter referred to as AFpixel row) in which the AF pixels constituting the AF pixel pairselected by the pixel selection unit 213 are arranged and a row ofpixels (hereinafter referred to as an imaging pixel row) in which the AFpixel is not arranged, and reads out a signal from each pixel. In thesecond readout mode, the readout unit 214 separately reads out signalsfrom the AF pixel row and from the imaging pixel row.

For example, the readout unit 214 reads out in the first readout mode ina case continuously shooting still images or in a case shooting ahigh-resolution moving image (for example, 4K moving image shooting).The readout unit 214 reads out in the second readout mode in a casedisplaying a through image on the display unit 24 or in a caseperforming low-resolution moving image shooting (for example, Full HDmoving image shooting). The first readout mode and the second readoutmode will be described later.

The focus detection unit 215 performs focus detection processingnecessary for automatic focus adjustment (AF) of the photographingoptical system 31. The focus detection unit 215 detects the focusposition (movement amount of the focusing lens 31 b to the focusingposition) for focusing (forming) the image formed by the photographingoptical system 31 on the imaging surface 22 a. The focus detection unit215 calculates the defocus amount by the pupil division type phasedifference detection method using the first and second signals Sig1 andSig2 of the AF pixel pair read out by the readout unit 214.

The focus detection unit 215 calculates an image shift amount byperforming correlation calculation with a first signal Sig1 generated bycapturing an image formed of a first light flux passed through a firstpupil region of the exit pupil of the photographing optical system 31and a second signal Sig2 generated by capturing an image formed of asecond light flux passed through a second pupil region of the exit pupilof the photographing optical system 31. The focus detection unit 215converts the image shift amount into a defocus amount based on apredetermined conversion formula. The focus detection unit 215calculates the movement amount of the focusing lens 31 b to the in-focusposition based on the calculated defocus amount.

The focus detection unit 215 determines whether or not the defocusamount is within the permissible value. If the defocus amount is withinthe permissible value, the focus detection unit 215 determines thatbeing an in-focus state. On the other hand, if the defocus amountexceeds the permissible value, the focus detection unit 215 determinesthat not being in-focus state and transmits signal for instructing themovement amount and moving operation of the focusing lens 31 b to thelens control unit 32 of the interchangeable lens 3. Focus adjustment isperformed automatically by the lens control unit 32 moving the focusinglens 31 b according to the movement amount.

Further, the focus detection unit 215 can also perform the focusdetection processing by the contrast detection method in addition to thefocus detection processing by the phase difference detection method. Thebody control unit 210 calculates the contrast evaluation value of thesubject image one after another based on the signal output from theimaging pixels while moving the focusing lens 31 b of the photographingoptical system 31 along the optical axis OA1 direction. The body controlunit 210 associates the position of the focusing lens 31 b and thecontrast evaluation value by using the position information of thefocusing lens 31 b transmitted from the interchangeable lens 3. Then,the body control unit 210 detects the position of the focusing lens 31 bat which shows the peak value of the contrast evaluation value, that is,the maximum value, as the in-focus position. The body control unit 210transmits information on the position of the focusing lens 31 bcorresponding to the detected focusing position to the lens control unit32. The lens control unit 32 moves the focusing lens 31 b to thein-focus position to perform the focus adjustment.

The image data generation unit 216 generates image data by performingvarious image processing on the signals read out from the imaging pixelsby the readout unit 214. It is to be noted that the image datageneration unit 216 may generate image data also using signals outputfrom the AF pixels.

FIG. 3 is a diagram showing an arrangement example of pixels in thefocus detection area 100. The R pixel 13, the G pixel 13, and the Bpixel 13 are arranged according to the Bayer arrangement. The first AFpixel 11 and the second AF pixel 12 are arranged by being replaced to apart of the imaging pixels 13 of the R, G, and B arranged in the Bayerarrangement. The first AF pixel 11 and the second AF pixel 12 each havea light-shielding portion 43. The position of the light-shieldingportion 43 in the first AF pixel 11 is different from the position ofthe light-shielding portion 43 in the second AF pixel 12.

As shown in FIG. 3 , the image sensor 22 has a pixel group (a firstimaging pixel row) 401 in which the R pixels 13 and the G pixels 13 arealternately arranged in left-right direction, that is, the rowdirection, and a pixel group (a second imaging pixel row) 402 in whichthe G pixels 13 and the B pixels 13 are alternately arranged in the rowdirection. Further, the image sensor 22 has a pixel group (a first AFpixel row) 403 in which the G pixels 13 and the first AF pixels 11 arealternately arranged in the row direction, and a pixel group (a secondAF pixel row) 404 in which the G pixels 13 and the second AF pixels 12are alternately arranged in the row direction.

In a first AF pixel row 403 a, the first AF pixels 11 a and the G pixels13 are alternately arranged. In a second AF pixel row 404 a, which isseparated from the first AF pixel row 403 a with a predetermined numberof rows, the second AF pixels 12 a and the G pixels 13 are alternatelyarranged. It is to be noted, the arrangement position of the first AFpixel 11 a in the first AF pixel row 403 a and the arrangement positionof the second AF pixel 12 a in the second AF pixel row 404 a are thesame as each other. That is, the first AF pixel 11 a and the second AFpixel 12 a are arranged in the same column. The first AF pixel 11 a ofthe first AF pixel row 403 a and the second AF pixel 12 a of the secondAF pixel row 404 a compose the first AF pixel pair.

In the first AF pixel row 403 b, which is separated from the second AFpixel row 404 a with a predetermined number of rows, the first AF pixels11 b and the G pixels 13 are alternately arranged. In the second AFpixel row 404 b, which is separated from the first AF pixel row 403 bwith a predetermined number of rows, the second AF pixels 12 b and the Gpixels 13 are alternately arranged. It is to be noted, the arrangementposition of the first AF pixel 11 b in the first AF pixel row 403 b andthe arrangement position of the second AF pixel 12 b in the second AFpixel row 404 b are the same as each other. That is, the first AF pixel11 b and the second AF pixel 12 b are arranged in the same column. Thefirst AF pixel 11 b of the first AF pixel row 403 b and the second AFpixel 12 b of the second AF pixel row 404 b compose the second AF pixelpair.

In the first AF pixel row 403 c, which is separated from the second AFpixel row 404 b with a predetermined number of rows, the first AF pixels11 c and the G pixels 13 are alternately arranged. In the second AFpixel row 404 c, which is separated from the first AF pixel row 403 cwith a predetermined number of rows, the second AF pixels 12 c and the Gpixels 13 are alternately arranged. It is to be noted, the arrangementposition of the first AF pixel 11 c in the first AF pixel row 403 c andthe arrangement position of the second AF pixel 12 c in the second AFpixel row 404 c are the same as each other. That is, the first AF pixel11 c and the second AF pixel 12 c are arranged in the same column. Thefirst AF pixel 11 c of the first AF pixel row 403 c and the second AFpixel 12 c of the second AF pixel row 404 c compose the third AF pixelpair.

It is to be noted, the first AF pixel row 403 a and the second AF pixelrow 404 a may be arranged in a plurality of rows, respectively, and aplurality of the first AF pixel pairs may be arranged. Further, thefirst AF pixel row 403 b and the second AF pixel row 404 b may bearranged in a plurality of rows, respectively, and a plurality of thesecond AF pixel pairs may be arranged. The first AF pixel row 403 c andthe second AF pixel row 404 c may be arranged in a plurality of rows,respectively, and a plurality of the third AF pixel pairs may bearranged.

As described above, the first, second and third AF pixel pairs arearranged so as to accurately detect defocus amount even if the exitpupil distance changes depending on an image height or a type of theinterchangeable lens. Accordingly, except for in the pixel pairsarranged around the optical axis OA1 (the center of the imaging surface22 a) of the photographing optical system 31, areas of thelight-shielding portions of the first, second and third AF pixel pairsare different to each other. Except for the AF pixels around the opticalaxis OA1 of the photographing optical system 31, the incident angles ofthe light incident on the AF pixels are different depending on the exitpupil distances being different. The incident angle increases as theexit pupil distance decreases, and the incident angle decreases as theexit pupil distance increases. The area of the light-shielding portion43 differs depending on the AF pixel pair in order to block a part ofthe light incident at different incident angles depending on the exitpupil distance. Thereby, the focus detection unit 215 can accuratelydetect the defocus amount even if the exit pupil distance differs. It isto be noted, with respect to the pixel pair around the optical axis OA1(center of the imaging surface 22 a) of the photographing optical system31, an incident angle is 0° in regardless of the exit pupil distance.Therefore, the areas of the light-shielding portions 43 of the first AFpixel pair, the second AF pixel pair, and the third AF pixel pair arethe same. As will be described later, the area of the light-shieldingportion 43 differs also depending on the position (image height) of theAF pixel.

Each of the first AF pixels 11 a, 11 b, 11 c and the second AF pixels 12a, 12 b, 12 c is provided with a filter having spectral characteristicsthat spectrally disperses the second wavelength region (green (G)) ofthe incident light. It is to be noted, the filter being provided witheach of the AF pixels of the first AF pixels 11 a to 11 c and the secondAF pixels 12 a to 12 c may have spectral characteristics that spectrallydisperses the first wavelength range (red (R) light) or the thirdwavelength range (blue (B) light). Alternatively, the first AF pixels 11a to 11 c and the second AF pixels 12 a to 12 c may have filters havingspectral characteristics that spectrally disperses the first, second,and third wavelength regions of the incident light.

FIG. 4 is a diagram for explaining a configuration example of an AFpixel and an imaging pixel provided in the image sensor 22 according tothe first embodiment. FIG. 4(a) shows an example of a cross section ofthe first AF pixel 11 among the first and second AF pixels 11 and 12constituting the AF pixel pair. FIG. 4(b) shows an example of a crosssection of the second AF pixel 12 among the first and second AF pixels11 and 12 constituting the AF pixel pair. FIG. 4(c) shows an example ofa cross section of the imaging pixel 13 (R pixel, G pixel, B pixel).

In FIG. 4 , each of the first and second AF pixels 11 and 12 and theimaging pixel 13 includes a microlens 44, a color filter 51, and aphotoelectric conversion unit 42 (PD42) which photoelectrically convertsthe light transmitted (passed) through the microlens 44 and the colorfilter 51. The first light flux 61 is a light flux that has passedthrough the first pupil region of the exit pupil of the photographingoptical system 31 among divided in substantially two equal regions. Thesecond light flux 62 is a light flux that has passed through the secondpupil region of the exit pupil of the photographing optical system 31among divided in substantially two equal regions.

In FIG. 4(a), the first AF pixel 11 is provided with a light-shieldingportion 43L that blocks the second light flux 62 among the first andsecond light fluxes 61 and 62. The light-shielding portion 43L isprovided, between the color filter 51 and the photoelectric conversionunit 42 and so as to position above the photoelectric conversion unit42. In the example shown in FIG. 4(a), the light-shielding portion 43Lis arranged so as to block the left half (−X direction side) of thephotoelectric conversion unit 42. The right end (end in the +Xdirection) of the light-shielding portion 43L substantially coincideswith the center line that bisects the photoelectric conversion portion42 to the left and right. The photoelectric conversion unit 42 of thefirst AF pixel 11 receives the first light flux 61. The photoelectricconversion unit 42 of the first AF pixel 11 photoelectrically convertsthe first light flux 61 to generate an electric charge, and the first AFpixel 11 outputs signal Sig1 based on the electric charge generated bythe photoelectric conversion unit 42.

The area of the light-shielding portion 43L differs depending on theposition (image height) of the first AF pixel 11, except for the firstAF pixel 11 around the optical axis OA1 (center of the imaging surface22 a) of the photographing optical system 31. If the position of thefirst AF pixel 11 differs, that is, the image height differs, theincident angle of the light incident to the first AF pixel 11 differs.If the image height increases, the incident angle increases, if theimage height decrease, the incident angle decreases, and if the imageheight is 0, the incident angle is 0°. The area of the light-shieldingportion 43L differs depending on the image height in order to block thesecond light flux 62 of the light incident at the incident angle thatdiffers depending on the image height.

In FIG. 4(b), the second AF pixel 12 is provided with a light-shieldingportion 43R that blocks the first light flux 61 among the first andsecond light fluxes 61 and 62. The light-shielding portion 43R isprovided, between the color filter 51 and the photoelectric conversionunit 42 and so as to position above the photoelectric conversion unit42. In the example shown in FIG. 4(b), the light-shielding portion 43Ris arranged so as to block the right half (+X direction side) of thephotoelectric conversion unit 42. The left end (end in the −X direction)of the light-shielding portion 43R substantially coincides with thecenter line that bisects the photoelectric conversion portion 42 to theleft and right. The photoelectric conversion unit 42 of the second AFpixel 12 receives the second light flux 62. The photoelectric conversionunit 42 of the second AF pixel 12 photoelectrically converts the secondlight flux 62 to generate an electric charge, and the second AF pixel 12outputs signal Sig2 based on the electric charge generated by thephotoelectric conversion unit 42.

Similarly to that of the first AF pixel 11, the area of thelight-shielding portion 43R differs depending on the position (imageheight) of the second AF pixel 12, except for the second AF pixel 12around the optical axis OA1 (center of the imaging surface 22 a) of thephotographing optical system 31. The area of the light-shielding portion43R differs depending on the image height in order to block the firstlight flux 61 of the light incident at the incident angle that differsdepending on the image height.

FIG. 4(c) shows that the photoelectric conversion unit 42 of the imagingpixel 13 receives the first and second light fluxes 61 and 62 that havepassed through the first and second pupil regions of the exit pupil ofthe photographing optical system 31. The photoelectric conversion unit42 of the imaging pixel 13 photoelectrically converts the first andsecond light fluxes 61 and 62 to generate an electric charge, and theimaging pixel 13 outputs signal based on the electric charge generatedby the photoelectric conversion unit 42.

FIG. 5 is a cross-sectional view of three types of AF pixel pairsarranged in a small region 110 a (see FIG. 2(b)) within the focusdetection area 100 a. FIG. 5(a) shows the first and second AF pixels 11a and 12 a constituting the first AF pixel pair arranged in the first AFpixel row 403 a and the second AF pixel row 404 a of FIG. 3 ,respectively. FIG. 5(b) shows the first and second AF pixels 11 b and 12b constituting the second AF pixel pair arranged in the first AF pixelrow 403 b and the second AF pixel row 404 b of FIG. 3 , respectively.FIG. 5(c) shows the first and second AF pixels 11 c and 12 cconstituting the third AF pixel pair arranged in the first AF pixel row403 c and the second AF pixel row 404 c of FIG. 3 , respectively. Asshown in FIG. 5 , in each of the first AF pixels 11 a to 11 c and thesecond AF pixels 12 a to 12 c, the center line of the photoelectricconversion unit 42 and the optical axis OA2 of the microlens 44substantially coincide. Light incident at an incident angle of 0° withrespect to the optical axis OA2 of the microlens 44 is focused on theoptical axis OA2 of the microlens. Since the line passing through thecenter of the photoelectric conversion unit 42 coincides with theoptical axis OA2 of the microlens 44, the light incident on themicrolens 44 is focused on the line passing through the center of thephotoelectric conversion unit 42. That is, the light transmitted throughthe photographing optical system 31 is focused on a line passing throughthe center of the photoelectric conversion unit 42.

In the first AF pixel 11 a shown in FIG. 5(a), the right end (end in the+X direction) of the light-shielding portion 43L substantially coincideswith the optical axis OA2 of the microlens 44. The light-shieldingportion 43L of the first AF pixel 11 a shields the left half (−Xdirection side) of the photoelectric conversion unit 42. The secondlight flux 62 transmitted through the microlens 44 is shielded by thelight-shielding portion 43L without being incident on the photoelectricconversion unit 42. Thereby, the photoelectric conversion unit 42 of thefirst AF pixel 11 a receives the first light flux 61. In the second AFpixel 12 a, the left end (end in the −X direction) of thelight-shielding portion 43R substantially coincides with the opticalaxis OA2 of the microlens 44. The first light flux 61 transmittedthrough the microlens 44 is shielded by the light-shielding portion 43Rwithout being incident on the photoelectric conversion unit 42. Thereby,the photoelectric conversion unit 42 of the second AF pixel 12 areceives the second light flux 62.

In each of the first AF pixels 11 b and 11 c shown in FIG. 5(b) and FIG.5(c), the right end (end in the +X direction) of the light-shieldingportion 43L substantially coincides with the optical axis OA2 of themicrolens 44. Therefore, each photoelectric conversion unit 42 of thefirst AF pixels 11 b and 11 c, similarly to that of the first AF pixel11 a, receives the first light flux 61. Further, in each of the secondAF pixels 12 b and 12 c, the left end (end in the −X direction) of thelight shielding portion 43R substantially coincides with the opticalaxis OA2 of the microlens 44. Therefore, similarly to the first AF pixel12 a, each photoelectric conversion unit 42 of the second AF pixels 12 band 12 c receives the second light flux 62.

FIG. 6 is a cross-sectional view of three types of AF pixel pairsarranged in a small region 110 c (see FIG. 2(b)) separated from thesmall region 110 a in the focus detection area 100 a in the +Xdirection. FIG. 6(a) shows the first and second AF pixels 11 a and 12 aconstituting the first AF pixel pair. FIG. 6(b) shows the first andsecond AF pixels 11 b and 12 b constituting the second AF pixel pair.FIG. 6(c) shows the first and second AF pixels 11 c and 12 cconstituting the third AF pixel pair.

As shown in FIG. 6 , in each of the first AF pixels 11 a to 11 c and thesecond AF pixels 12 a to 12 c, a line passing through the center of thephotoelectric conversion unit 42 is being shifted in the +X directionwith respect to the optical axis OA2 of the microlens 44. In the presentembodiment, in the first and second AF pixels arranged apart from thesmall region 110 a in the +X direction, the line passing through thecenter of the photoelectric conversion unit 42 is being shifted in the+X direction with respect to the optical axis OA2 of the microlens 44.Further, in the first and second AF pixels arranged apart from the smallregion 110 a in the −X direction, the line passing through the center ofthe photoelectric conversion unit 42 is being shifted in the −Xdirection with respect to the optical axis OA2 of the microlens 44.

As shown in FIG. 6 , the areas of the light-shielding portions 43L ofthe first AF pixels 11 a to 11 c are different to each other. The areaof the light-shielding portion 43L of the first AF pixel 11 a is smallerthan the area of the light-shielding portion 43L of the first AF pixel11 b. The area of the light-shielding portion 43L of the first AF pixel11 b is smaller than the area of the light-shielding portion 43L of thefirst AF pixel 11 c. The areas of the light-shielding portions 43R ofthe second AF pixels 12 a to 12 c are different to each other. The areaof the light-shielding portion 43R of the second AF pixel 12 a is largerthan the area of the light-shielding portion 43R of the second AF pixel12 b. The area of the light-shielding portion 43R of the second AF pixel12 b is larger than the area of the light-shielding portion 43R of thesecond AF pixel 12 c.

As shown in FIG. 6 , the line passing through the center line of thephotoelectric conversion unit 42 and the optical axis OA2 of themicrolens 44 are deviated, and the area of the light-shielding portions43 of the first AF pixel and the area of the light-shielding portions 43of the second AF pixel are different. Thus, in each of the first andsecond AF pixels, the edge of the light-shielding portion and theoptical axis OA2 of the microlens 44 are deviated from each other. InFIG. 6(a), for example, in the first AF pixel 11 a, the right end (endin the +X direction) of the light-shielding portion 43L is located onthe +X direction side by the deviation amount d1 from the optical axisOA2 of the microlens 44. Further, in the second AF pixel 12 a, the leftend (end in the −X direction) of the light-shielding portion 43R islocated on the +X direction side by the deviation amount d1 from theoptical axis OA2 of the microlens 44.

As shown in FIG. 6 , each of the deviation amounts in the second andthird AF pixel pairs is different from the deviation amount in the firstAF pixel pair. The deviation amount d2 in the first and second AF pixels11 b and 12 b constituting the second AF pixel pair is larger than thedeviation amount d1 in the first and second AF pixels 11 a and 12 aconstituting the first AF pixel pair. The deviation amount d3 in thefirst and second AF pixels 11 c and 12 c constituting the third AF pixelpair is larger than the deviation amount d2 in the first and second AFpixels 11 b and 12 b constituting the second AF pixel pair. That is,d1<d2<d3.

FIG. 7 is a cross-sectional view of three types of AF pixel pairs in apart of the focus detection area 100 c separated from the focusdetection region 100 a shown in FIG. 2 in the +X direction. FIG. 7(a)shows the first and second AF pixels 11 a and 12 a constituting thefirst AF pixel pair. FIG. 7(b) shows the first and second AF pixels 11 band 12 b constituting the second AF pixel pair. FIG. 7(c) shows thefirst and second AF pixels 11 c and 12 c constituting the third AF pixelpair.

Similarly to the three types of AF pixel pairs shown in FIG. 6 , in eachof the first AF pixels 11 a to 11 c and the second AF pixels 12 a to 12c shown in FIG. 7 , a line passing through the center of thephotoelectric conversion unit 42 is being shifted in the +X directionwith respect to the optical axis OA2 of the microlens 44. Further,similarly to the three types of AF pixel pairs shown in FIG. 6 , theareas of the light-shielding portions 43L of the first AF pixels 11 a to11 c are different to each other. Also, the areas of the light-shieldingportions 43R of the second AF pixels 12 a to 12 c are different to eachother.

In the three types of AF pixel pairs shown in FIG. 6 and FIG. 7 , eachof the amounts of deviation of the line passing through the center ofthe photoelectric conversion unit 42 with respect to the optical axisOA2 of the microlens 44 differs to each other. Further, in the AF pixelsother than the first AF pixel 11 b and the second AF pixel 12 b, thearea of the light-shielding portion 43L and the area of thelight-shielding portion 43R are different. Compared with the three typesof AF pixel pairs shown in FIG. 6 , the three types of AF pixel pairsshown in FIG. 7 have a larger deviation amount with respect to theoptical axis OA2 of the microlens 44. Further, as compared with thefirst AF pixel 11 a and the second AF pixel 12 a shown in FIG. 6 , thefirst AF pixel 11 a and the second AF pixel 12 a shown in FIG. 7respectively have a smaller area of the light-shielding portion 43L anda larger area of the light-shielding portion 43R. As compared with thefirst AF pixel 11 c and the second AF pixel 12 c shown in FIG. 6 , thefirst AF pixel 11 c and the second AF pixel 12 c shown in FIG. 7respectively have a larger area of the light-shielding portion 43L and asmaller area of the light-shielding portion 43R. The areas of thelight-shielding portion 43L and the light-shielding portion 43R in eachof the first AF pixel 11 b and the second AF pixel 12 b shown in FIG. 7are the same as the areas of those shown in FIG. 6 .

In the first AF pixel 11 a, the right end (end in the +X direction) ofthe light-shielding portion 43L is deviated by the amount d4 in the +Xdirection with respect to the optical axis OA2 of the microlens 44. Inthe second AF pixel 12 a, the left end (end in the −X direction) of thelight-shielding portion 43R is deviated by the amount d4 in the +Xdirection with respect to the optical axis OA2 of the microlens 44.

Each of the deviation amounts in the second and third AF pixel pairs isdifferent from the deviation amount in the first AF pixel pair. Thedeviation amount d5 in the first and second AF pixels 11 b and 12 bconstituting the second AF pixel pair is larger than the deviationamount d4 in the first and second AF pixels 11 a and 12 a constitutingthe first AF pixel pair. The deviation amount d6 in the first and secondAF pixels 11 c and 12 c constituting the third AF pixel pair is largerthan the deviation amount d5 in the first and second AF pixels 11 b and12 b constituting the second AF pixel pair. That is, d4<d5<d6.

As shown in FIG. 5 , FIG. 6 and FIG. 7 , the deviation amount betweenthe line passing through the center of the photoelectric conversion unit42 and the optical axis OA2 of the microlens 44 differs depending on theimage height. The higher the image height, the larger the deviationamount, and the lower the image height, the smaller the deviationamount. At a position where the image height is high, light passesthrough the photographing optical system 31 and is obliquely incident tothe microlens 44. That is, the light is incident at an incident anglelarger than 0° with respect to the optical axis OA2 of the microlens 44.Therefore, it can also be said that the larger the incident angle oflight with respect to the microlens 44, the larger the deviation amount.Incident light having an incident angle larger than 0° with respect tothe optical axis OA2 of the microlens 44 is focused as shifting in the+X direction or −X direction from the optical axis OA2 of the microlens.Because the line passing through the center of the photoelectricconversion unit 42 and the optical axis OA2 of the microlens 44 deviatefrom each other, the light incident on the microlens 44 is focused onthe line passing through the center of the photoelectric conversion unit42. That is, the light transmitted through the photographing opticalsystem 31 is focused on a line passing through the center of thephotoelectric conversion unit 42. Thereby, the amount of lighttransmitted through the photographing optical system 31 and incident onthe photoelectric conversion unit 42 can be increased.

As shown in FIG. 5 , FIG. 6 and FIG. 7 , the area of the light-shieldingportion 43 differs depending on the AF pixel pair. As described above,the exit pupil distance of the photographing optical system 31 differsdepending on the type of the interchangeable lens 3. Therefore, each ofthe first AF pixel pair, the second AF pixel pair, and the third AFpixel pair has a light-shielding portion 43 having a different area inorder to accurately detect the defocus amount at different exit pupildistances. Further, the area of the light-shielding portion 43L and thearea of the light-shielding portion 43R of the first AF pixel pairdiffer depending on the position (image height) where the first AF pixelpair is arranged. As described above, the exit pupil distance of thephotographing optical system 31 differs depending on the image height.Therefore, the first AF pixel pair has a light-shielding portion 43L anda light-shielding portion 43R having an area that differs depending onthe image height in order to accurately detect the defocus amount atdifferent exit pupil distances. The same applies to the third AF pixelpair as in the first AF pixel pair. Thereby, the focus detection unit215 can accurately detect the defocus amount even at different exitpupil distances. That is, the focus detection unit 215 can accuratelydetect the defocus amount even if the image height or the type of theinterchangeable lens changes.

In the first to third AF pixel pairs, the deviation amount between thelight-shielding portion 43 and the optical axis of the microlens 44increases as the image height increases in the +X direction from thesmall region 110 a shown in FIG. 2(b). Comparing the deviation amountsof the first to third AF pixel pairs in the three regions where theimage heights are Ha, Hb, and Hc (Ha<Hb<Hc) is as follows. The deviationamount in the first AF pixel pair at the region of image height Hb islarger than the deviation amount in the first AF pixel pair at theregion of image height Ha, and is smaller than the deviation amount inthe first AF pixel pair at the region of image height Hc. Similarly, thedeviation amount in each the second and third AF pixel pairs at theregion of image height Hb is respectively larger than the deviationamount in each the second and third AF pixel pairs at the region ofimage height Ha, and is respectively smaller than the deviation amountin each the second and third AF pixel pairs at the region of imageheight Hc. The deviation amount d4 in the first AF pixel pair arrangedin the focus detection area 100 c shown in FIG. 7 is larger than thedeviation amount d1 in the first AF pixel pair arranged in the smallregion 110 c shown in FIG. 6 . The deviation amounts d5 and d6 in thesecond and third AF pixel pairs arranged in the focus detection region100 c shown in FIG. 7 are respectively larger than the deviation amountsd2 and d3 in the second and third AF pixel pairs arranged in the smallregion 110 c shown in FIG. 6 .

To the first to third AF pixel pairs arranged in the small region 110 bseparated from the small region 110 a shown in FIG. 2(b) in the −Xdirection, deviation amounts of the same amount as d1 to d3 arerespectively given in the direction opposite to the deviation directionshown in FIG. 6 . To the first to third AF pixel pairs arranged in thesmall region 110 b shown in FIG. 2(a), deviation amounts of the sameamount as d4 to d6 are respectively given in the direction opposite tothe deviation direction shown in FIG. 7 . The deviation amount in thefirst to third AF pixel pairs arranged apart from the small region 110 ain the −X direction also increases as the image height increases.

As described above, the deviation amounts in the first to third AF pixelpairs are different from each other. Therefore, on the surfacesintersecting in the light incident direction, the areas of lightreceiving portions of the photoelectric conversion units 42 in each ofthe first AF pixels 11 a to 11 c are different from each other, and theareas of light receiving portions of the photoelectric conversion units42 in each of the second AF pixels 12 a to 12 c are different from eachother. As described above, in the present embodiment, since the lightreceiving areas of the photoelectric conversion units 42 are differentfrom each other in the first to third AF pixel pairs, it is possible toperform pupil division corresponding to different incident angles. As aresult, the focus detection unit 215 can accurately detect the defocusamount.

Next, an example of a method for determining the deviation amounts inthe first to third AF pixel pairs in the focus detection area 100 willbe described. In FIG. 8, 110 a represents the position of the smallregion 110 located at a distance corresponding to the image height Hdfrom the position 0 (the center position of the imaging surface 22 a)where the optical axis OA1 of the photographing optical system 31intersects the imaging surface 22 a of the image sensor 22. A firstreference exit pupil EP1, a second reference exit pupil EP2, and a thirdreference exit pupil EP3 are set on the optical axis OA1 of thephotographing optical system 31. The second reference exit pupil EP2exists closer to the imaging surface 22 a than the first reference exitpupil EP1 and exists to the +Z direction side than the first referenceexit pupil EP1. The third reference exit pupil EP3 exists closer to theimaging surface 22 a than the second reference exit pupil EP2 and existsto the +Z direction side than the second reference exit pupil EP2.

The distance between the first reference exit pupil EP1 and the imagingsurface 22 a is defined as the first reference exit pupil distance Po1,the distance between the second reference exit pupil EP2 and the imagingsurface 22 a is defined as the second reference exit pupil distance Po2,and the distance between the third reference exit pupil EP3 and theimaging surface 22 a is defined as the third reference exit pupildistance Po3. It is to be noted that Po1>Po2>Po3.

In FIG. 8 , L1 indicates the principal ray of the light flux that passesthrough the first reference exit pupil EP1 and is incident on the AFpixel in the small region 110 at the position 110α. L2 indicates theprincipal ray of the light flux that passes through the second referenceexit pupil EP2 and is incident on the AF pixel in the small region 110at the position 110α. L3 indicates the principal ray of the light fluxthat passes through the third reference exit pupil EP3 and is incidenton the AF pixel in the small region 110 at the position 110α.

In FIG. 8 , assuming that θ1 is the angle of incidence of the principalray L1 to the AF pixel, the deviation amount in the first AF pixel pairin the small region 110 at the image height Hd is determined based onthe angle of incidence θ1. Similarly, assuming that θ2 and θ3respectively are the angles of incidence of the principal rays L2 and L3to the AF pixels, the deviation amounts in the second and third AF pixelpairs in the small region 110 at the image height Hd are determinedbased on the angles of incidence θ2 and θ3, respectively. As describedabove, the deviation amount increases as the incident angle increases.Further, except for the position where the image height is 0 (position0), the longer the exit pupil distance, the smaller the incident angle,so that θ1<θ2<θ3. Therefore, in the first, second, and third AF pixelpairs shown in FIGS. 6(a) through 6(c), the deviation amounts d1, d2,and d3 are as d1<d2<d3. Further, in the first, second, and third AFpixel pairs shown in FIGS. 7(a) through 7(c), the deviation amounts d4,d5, and d6 are as d4<d5<d6.

In such a way, the deviation amount of the first AF pixel pair withrespect to the first reference exit pupil EP1 (the first reference exitpupil distance Po1) is determined. Similarly, the deviation amount ofthe second AF pixel pair with respect to the second reference exit pupilEP2 (the second reference exit pupil distance Po2) and the deviationamount of the third AF pixel pair with respect to the third referenceexit pupil EP3 (the third reference exit pupil distance Po3) aredetermined.

Next, the relationship between the exit pupil distance of thephotographing optical system 31 and the first to third AF pixel pairswill be described. As shown in FIG. 8 , a first threshold value Th1regarding the exit pupil distance is set at an intermediate positionbetween the first reference exit pupil EP1 and the second reference exitpupil EP2, and a second threshold value Th2 regarding the exit pupildistance is set at an intermediate position between the second referenceexit pupil EP2 and the third reference exit pupil EP3. The region wherethe exit pupil distance is equal to or greater than the first thresholdTh1 is defined as a first exit pupil distance range R1, the region wherethe exit pupil distance is between the first threshold Th1 and thesecond threshold Th2 is defined as a second exit pupil distance rangeR2, and the region where the exit pupil distance is equal to or lessthan the second threshold Th2 is defined as a third exit pupil distancerange R3.

In a case that the exit pupil distance of the photographing opticalsystem 31 is equal to or greater than the first threshold Th1, that is,in a case that the exit pupil distance of the photographing opticalsystem 31 belongs to the first exit pupil distance range R1, the pixelselection unit 213 selects the first AF pixel pair. In a case that theexit pupil distance of the photographing optical system 31 is betweenthe first threshold Th1 and the second threshold Th2, that is, in a casethat the exit pupil distance of the photographing optical system 31belongs to the second exit pupil distance range R2, the pixel selectionunit 213 selects the second AF pixel pair. In a case that the exit pupildistance of the photographing optical system 31 is equal to or less thanthe second threshold Th2, that is, in a case that the exit pupildistance of the photographing optical system 31 belongs to the thirdexit pupil distance range R3, the pixel selection unit 213 selects thethird AF pixel pair.

As described above, the pixel selection unit 213 selects an appropriateAF pixel pair from the first to third AF pixel pairs depending on, whichthe exit pupil distance of the photographing optical system belongs toamong the first to third exit pupil distance ranges R1 to R3.

Next, the optical characteristics of the photographing optical system 31of the interchangeable lens 3, specifically, the optical characteristicsin which the exit pupil distance thereof changes depending on the imageheight will be described. FIG. 9 shows the optical characteristics ofthe interchangeable lens 3 to be mounted on the camera body 2 shown inFIG. 1 in which the exit pupil distance changes depending on the imageheight. In FIG. 9 , the horizontal axis represents the exit pupildistance Po, and the vertical axis represents the image height H. FIG.9(a), FIG. 9(b), FIG. 9(c), and FIG. 9(d) respectively show the opticalcharacteristics of different types of interchangeable lenses. Withrespect to the optical characteristics of the photographing opticalsystem 31 of the interchangeable lens 3, which is represented by theoptical characteristic curve 200 a in FIG. 9(a), the exit pupil distancePo decreases as the image height H increases. The optical characteristiccurve 200 a in FIG. 9(a) shows that, the exit pupil distance is Poa atimage height zero, the exit pupil distance gradually decreases as theimage height H increases, and the exit pupil distance becomes (Poa−Δp1)at the maximum image height Hmax.

With respect to the optical characteristics of the photographing opticalsystem 31 of the interchangeable lens 3, which is represented by theoptical characteristic curve 200 b in FIG. 9(b), the exit pupil distancePo increases as the image height H increases. The optical characteristiccurve 200 b in FIG. 9(b) shows that, the exit pupil distance is Pob atimage height zero, the exit pupil distance gradually increases as theimage height H increases, and the exit pupil distance becomes (Pob+Δp2)at the maximum image height Hmax.

In the following description, an optical characteristic curve in whichthe exit pupil distance Po decreases as the image height H increases,such as the optical characteristic curve 200 a, is referred to as anegative optical characteristic curve. On the other hand, an opticalcharacteristic curve in which the exit pupil distance Po increases asthe image height H increases, such as the optical characteristic curve200 b, is referred to as a positive optical characteristic curve.

The photographing optical system 31 of the interchangeable lens 3 shownin FIG. 9 (c) has an optical characteristic curve that differs, that is,changes depending on the position of the focusing lens 31 b shown inFIG. 1 . This photographing optical system 31 exhibits an opticalcharacteristic curve 200 c when the focusing lens 31 b is located at afirst position and exhibits an optical characteristic curve 200 d whenthe focusing lens 31 b is located at a second position. The first andsecond positions of the focusing lens 31 b are arbitrary positionsbetween the infinity position and the closest position, of the focusinglens 31 b, including the infinity position and the closest position. Theinfinity position of the focusing lens 31 b is a position where thesubject at the infinity distance is in focus, and the closest positionis a position where the subject at the closest distance is in focus.

In FIG. 9(c), the optical characteristic curve 200 c represents theoptical characteristics of the photographing optical system 31 in a casewhere the focusing lens 31 b is at the first position. The opticalcharacteristic curve 200 c shows that, the exit pupil distance is Poc atimage height zero, the exit pupil distance gradually decreases as theimage height H increases, and the exit pupil distance becomes (Poc−Δp3)at the maximum image height Hmax. The optical characteristic curve 200 drepresents the optical characteristics of the photographing opticalsystem 31 in a case where the focusing lens 31 b is at the secondposition. The optical characteristic curve 200 d shows that, the exitpupil distance is Pod at image height zero, the exit pupil distancegradually increases as the image height H increases, and the exit pupildistance becomes (Pod+Δp4) at the maximum image height Hmax.

In FIG. 9(c), the optical characteristic curve 200 c in the case wherethe focusing lens 31 b is at the first position is shown as the negativeoptical characteristic curve, and the optical characteristic curve 200 din the case where the focusing lens 31 b is at the second position isshown as the positive optical characteristic curve. However, there canalso be an interchangeable lens 3 having an optical characteristic inwhich both the optical characteristic curve 200 c and the opticalcharacteristic curve 200 d are both positive or negative.

The photographing optical system 31 of the interchangeable lens 3 shownin FIG. 9(d) has an optical characteristic curve that differs, that is,changes depending on the focal length of the zoom lens (the position ofthe zoom lens 31 a in FIG. 1 ). This photographing optical system 31exhibits an optical characteristic curve 200 e in a case where both thefocal length is f1 and exhibits an optical characteristic curve 200 f ina case where the focal length is f2.

In FIG. 9(d), the optical characteristic curve 200 e represents theoptical characteristics of the photographing optical system 31 in a casewhere the focal length is f1. The optical characteristic curve 200 eshows that, the exit pupil distance is Poe at image height zero, theexit pupil distance gradually decreases as the image height H increases,and the exit pupil distance becomes (Poe−Δp5) at the maximum imageheight Hmax. The optical characteristic curve 200 f represents theoptical characteristics of the photographing optical system 31 in a casewhere the focal length is f2. The optical characteristic curve 200 fshows that, the exit pupil distance is Pof at image height zero, theexit pupil distance gradually increases as the image height H increases,and the exit pupil distance becomes (Pof+Δp6) at the maximum imageheight Hmax.

In FIG. 9(d), the optical characteristic curve 200 e in the case wherethe focal length is f1 is shown as the negative optical characteristiccurve, and the optical characteristic curve 200 f in the case where thefocal length is f2 is shown as the positive optical characteristiccurve. However, there can also be an interchangeable lens 3 having anoptical characteristic in which both the optical characteristic curve200 e and the optical characteristic curve 200 f are both positive ornegative.

It is to be noted that the exit pupil distance Po at the image height Hin the above description is the distance of the exit pupil of thephotographing optical system 31 from view of the image height H of theimaging surface 22 a. In other words, the exit pupil distance Po at theimage height H is the exit pupil distance (distance from the imagingsurface 22 a) of the photographing optical system 31 through which thelight flux that passes through the photographing optical system 31 andis incident on the position in correspondence with the image height H ofthe imaging surface 22 a.

FIG. 10 is a diagram showing the relationship between the image height Hand the exit pupil distance Po. In FIG. 10 , to the AF pixel (in FIG. 10, the microlens 44 is shown on behalf of the AF pixel) located at thecenter position 0 (image height zero) of the imaging surface 22 a, thelight flux that has passed through the exit pupil EPa (exit pupildistance Poa) of the imaging optical system 31 is incident. The exitpupil distance Poa of this exit pupil EPa is the exit pupil distance ofthe exit pupil EPa for the image height zero.

Further, a light flux that has passed through the exit pupil EPb of thephotographing optical system 31 is incident on the AF pixel (in FIG. 10, the microlens 44 is shown as representative of the AF pixel) locatedat the image height He. The exit pupil distance (Poa−Δp) of the exitpupil EPb is the exit pupil distance of the exit pupil EPb for the imageheight H.

Here, the relationship between the optical characteristics of eachinterchangeable lens 3 and the above formula (1) will be described. Po(H)=h4×H⁴+h2×H²+Co of the above formula (1) is a function to approximatethe optical characteristic curves 200 a, 200 b, 200 c, 200 d, 200 e, 200f and the like shown in FIG. 9 (a) through FIG. 9 (d). The opticalcharacteristic curve 200 a shown in FIG. 9(a) is approximated by thecalculation of the formula (1); by setting the constant term Co to theexit pupil distance Poa at the image height zero of FIG. 9(a), and bysetting the coefficients h4 and h2 to the coefficients h4 a and h2 acorresponding to the curve of the optical characteristic curve 200 a. Asdescribed above, the interchangeable lens 3 having the opticalcharacteristics of FIG. 9(a) stores the constant term Poa and thecoefficients h4 a and h2 a in the lens memory 33 as lens information.

Similarly, with respect to the interchangeable lens 3 having the opticalcharacteristics of FIG. 9(b), the constant terms Pob and thecoefficients h4 b and h2 b, that determines a calculation of the formula(1) that approximates the optical characteristics curve 200 b are storedin the lens memory 33 as the lens information.

Further, the interchangeable lens 3 shown in FIG. 9(c) has opticalcharacteristics in which the optical characteristic curve changesdepending on the position of the focusing lens 31 b. The interchangeablelens 3 stores in the lens memory 33 the constant terms Co and thecoefficients h4 and h2 for the calculation of the formula (1) thatapproximate the optical characteristic curve for each position of thefocusing lens 31 b. The range in which the focusing lens 31 b moves(between the infinity position and the closest position) is divided intoa plurality of zones Z1 to Zn, and one optical characteristic curverepresenting the zone (range) is determined for each section Z1 to Zn.For example, the optical characteristic curve in a case where thefocusing lens 31 b is located at the intermediate position of one zoneis defined as the optical characteristic curve representing that zone.

The optical characteristic curve representing the zone Zk is defined asthe optical characteristic curve Zk (k=1, 2, . . . n). For thecalculation of the formula (1) that approximates the opticalcharacteristic curve Z1 representing the zone Z1, the constant term Coand the coefficients h4 and h2 are set to Poz1, h4 z 1 and h2 z 1. Forthe calculation of the formula (1) that approximates the opticalcharacteristic curve Z2 representing the zone Z2, the constant term Coand the coefficients h4 and h2 are set to Poz2, h4 z 2 and h2 z 2.Similarly, for the calculation of the formula (1) that approximates theoptical characteristic curve Zn representing the zone Zn, the constantterm Co and the coefficients h4 and h2 are set to Pozn, h4 zn and h2 zn.FIG. 11 shows these zones and the constant terms and coefficients forthe calculation for approximating the optical characteristic curvesrepresenting these zones. The interchangeable lens 3 stores the zones Z1to Zn, the constant terms Poz1 to Pozn, and the coefficients h4 z 1 toh4 zn and h2 z 1 to h2 zn shown in FIG. 11 in the lens memory 33, aslens information.

The interchangeable lens 3 shown in FIG. 9(d) is a zoom lens and hasoptical characteristics in which the optical characteristic curvechanges depending on the focal length. The interchangeable lens 3 storesin the lens memory 33 the constant terms Co and the coefficients h4 andh2 for the calculation of the formula (1) that approximate the opticalcharacteristic curve for each focal length. The distance between themaximum focal length and the minimum focal length of the zoom lens setby the zoom lens 31 a shown in FIG. 1 is divided into a plurality ofzones W1 to Wn, and one optical characteristic curve representing thezone is determined for each zone W1 to Wn. For example, an opticalcharacteristic curve at a focal length in the middle of one zone isdefined as an optical characteristic curve representing that zone.

The optical characteristic curve representing the zone Wk is defined asthe optical characteristic curve Wk (k=1, 2, . . . n). For thecalculation of the formula (1) that approximates the opticalcharacteristic curve W1 representing the zone W1, the constant term Coand the coefficients h4 and h2 are set to Pow1, h4 w 1 and h2 w 1. Forthe calculation of the formula (1) that approximates the opticalcharacteristic curve W2 representing the zone W2, the constant term Coand the coefficients h4 and h2 are set to Pow2, h4 w 2 and h2 w 2.Similarly, for the calculation of the formula (1) that approximates theoptical characteristic curve Wn representing the zone Wn, the constantterm Co and the coefficients h4 and h2 are set to Pown, h4 wn and h2 wn.FIG. 12 shows these zones and the constant terms and coefficients forthe calculation for approximating the optical characteristic curvesrepresenting these zones. The interchangeable lens 3 stores the zones W1to Wn, the constant terms Pow1 to Pown, the coefficients h4 w 1 to h4wn, and h2 w 1 to h2 wn in the lens memory 33 shown in FIG. 12 , as lensinformation.

Although the interchangeable lens 3 of FIG. 9(d) is a zoom lens havingoptical characteristics in which the optical characteristic curvechanges depending on the focal length, there is another zoom lens havingoptical characteristics in which the optical characteristic curvechanges depending on the position of the focusing lens 31 b in additionthat the optical characteristic curve changes depending on the focallength. That is, the optical characteristic curve of the another zoomlens changes depending on both the position (focal length) of the zoomlens 31 a and the position of the focusing lens 31 b.

Next, the relationship between the optical characteristic curve showingthe optical characteristics of the interchangeable lens 3 shown in FIG.9 and the first to third exit pupil distance ranges R1 to R3 shown inFIG. 8 will be described. FIG. 13 shows; the first and second thresholdvalues Th1 and Th2 regarding the exit pupil distance shown in FIG. 8 ,the first to third exit pupil distance ranges R1 to R3, and the opticalcharacteristic curve exemplified in FIG. 9 . As shown in FIG. 13 , inthe entire optical characteristic curve 200 g, that is, the exit pupildistance from the image height zero to the maximum image height Hmax islocated within the second exit pupil distance range R2. In a case wherethe interchangeable lens 3 having such an optical characteristic curve200 g is attached to the camera body 2, even if the region setting unit211 set the focus detection area 100 for any image height H, the pixelselection unit 213 selects the second AF pixel pair.

With respect to the optical characteristic curve 200 h, the partcorresponding to the exit pupil distance from the image height zero tothe image height Hf belongs to the second exit pupil distance range R2,and the part corresponding to the exit pupil distance from the imageheight Hf to the maximum image height Hmax belongs to the first exitpupil distance range R1. In a case where the area setting unit 211 setsthe focus detection area 100 at which the image height is Hf or less,the pixel selection unit 213 selects the second AF pixel pair. Further,in a case where the area setting unit 211 sets the focus detection area100 at which the image height is larger than Hf, the pixel selectionunit 213 selects the first AF pixel pair.

With respect to the optical characteristic curve 200 i, the partcorresponding to the exit pupil distance from the image height zero tothe image height Hg belongs to the third exit pupil distance range R3,and the part corresponding to the exit pupil distance from the imageheight Hg to the maximum image height Hmax belongs to the second exitpupil distance range R2. In a case where the area setting unit 211 setsthe focus detection area 100 at which the image height is Hg or less,the pixel selection unit 213 selects the third AF pixel pair. Further,in a case where the area setting unit 211 sets the focus detection area100 at which the image height is larger than Hg, the pixel selectionunit 213 selects the second AF pixel pair.

It is to be noted, as described above, in a case where a plurality offocus detection areas 100 are set by the area setting unit 211, thepixel selection unit 213 selects the same type of AF pixel pairs for allselected focus detection area 100. In such case, the pixel selectionunit 213 selects an AF pixel pair based on the position of the focusdetection area 100 farthest from the optical axis OA1 of thephotographing optical system 31 (the image height H is the highest)among the plurality of selected focus detection areas 100. In thepresent embodiment, the pixel selection unit 213 selects AF pixel pairsas described above based on the image height of the focus detection area100 having the highest image height among the plurality of selectedfocus detection areas 100. The pixel selection unit 213 selects AF pixelpairs of the same type as the selected AF pixel pair for the focusdetection area 100 of the highest image height among the selectedplurality of focus detection areas 100 with respect also to other focusdetection areas 100.

The circuit configuration and operation of the image sensor 22 accordingto the first embodiment will be described with reference to FIG. 14 andFIG. 15 . FIG. 14 is a diagram showing a configuration of a pixel of theimage sensor 22 according to the first embodiment. The pixel 13 includesthe photoelectric conversion unit 42, a transfer unit 52, a reset unit53, a floating diffusion (FD) 54, an amplification unit 55, and aselection unit 56. The photoelectric conversion unit 42 is a photodiodePD, which converts incident light into electric charge and stores thephotoelectrically converted electric charges.

The transfer unit 52 is configured with a transistor M1 controlled by asignal TX, and transfers the charge photoelectrically converted by thephotoelectric conversion unit 42 to the FD 54. The transistor M1 is atransfer transistor. A capacitor C of the FD 54 accumulates (retains)the charge transferred to the FD 54.

The amplification unit 55 outputs a signal corresponding to the electriccharge stored in the capacitor C of the FD 54. The amplification unit 55and the selection unit 56 configure an output unit that generates andoutputs a signal based on the electric charge generated by thephotoelectric conversion unit 42.

The reset unit 53 is configured with a transistor M2 controlled by asignal RST, discharges the electric charge accumulated in the FD 54, andresets the voltage of the FD 54. The transistor M2 is a resettransistor.

The selection unit 56 is configured with a transistor M4 controlled by asignal SEL, and electrically connects or disconnects the amplificationunit 55 and a vertical signal line 60. The transistor M4 is a selectiontransistor.

As described above, the charge photoelectrically converted by thephotoelectric conversion unit 42 is transferred to the FD 54 by thetransfer unit 52. Then, a signal corresponding to the electric chargetransferred to the FD 54 is output to the vertical signal line 60. Apixel signal is an analog signal generated based on the electric chargephotoelectrically converted by the photoelectric conversion unit 42. Thesignal output from the imaging pixel 13 is converted into a digitalsignal and then output to the body control unit 210.

It is to be noted, in the present embodiment, the circuit configurationsof the first AF pixels 11 (11 a to 11 c) and the second AF pixels 12 (12a to 12 c) are the same as the circuit configuration of the imagingpixel 13. The signals output from the first AF pixel 11 and the secondAF pixel 12 are converted into digital signals and then output to thebody control unit 210 as the pair of signals (the first and secondsignals Sig1 and Sig2) used for focus detection.

FIG. 15 is a diagram showing a configuration example of the image sensoraccording to the first embodiment. The image sensor 22 includes aplurality of imaging pixels 13, a first AF pixel 11 and a second AFpixel 12, a vertical control unit 70, and a plurality of column circuitunits 80. It is to be noted, in FIG. 15 , for simplification of thedescription, only 128 pixels of 8 pixels in the row direction (±Xdirection)×16 pixels in the column direction (±Y direction) are shown.In FIG. 15 , the pixel in the upper left corner is defined as theimaging pixel 13 (1,1) in the 1st row and the 1st column, and theimaging pixel in the lower right corner is defined as the imaging pixel13 (16, 8) in the 16th row and the 8th column. The image sensor 22 isprovided with a plurality of vertical signal lines 60 (vertical signallines 60 a to 60 h). The plurality of vertical signal lines 60 areconnected to each of the pixel columns (1st column to 8th column), whichis a column of a plurality of pixels arranged in the column direction,that is, in the vertical direction. To each of the vertical signal lines60 a, 60 c, 60 e, 60 g, a plurality of imaging pixels 13 arranged ineach of columns are connected, and the vertical signal lines 60 a, 60 c,60 e, 60 g respectively output signals of the connected imaging pixels13. To each of the vertical signal lines 60 b, 60 d, 60 f, 60 h, aplurality of imaging pixels 13, a plurality of the first AF pixels and aplurality of the second AF pixels arranged in each of columns areconnected, and the vertical signal lines 60 b, 60 d, 60 f, 60 hrespectively output signals of the connected imaging pixels 13, thefirst AF pixels and the second AF pixels.

The vertical control unit 70 is provided so as to be common to aplurality of pixel columns. The vertical control unit 70 supplies thesignal TX, the signal RST, and the signal SEL shown in FIG. 14 to eachpixel to control the operation of each pixel. The vertical control unit70 supplies a signal to the gate of each transistor of the pixel, andturns the transistor on (connected state, conducting state,short-circuited state) or off state (disconnected state, non-conductingstate, open state, break-circuit state).

The column circuit unit 80 includes an analog/digital conversion unit(AD conversion unit), and converts an analog signal input from eachpixel via the vertical signal line 60 into a digital signal and outputsthe converted signal. The pixel signal converted into a digital signalis input to a signal processing unit (not shown), and after signalprocessing such as correlation double sampling and processing forcorrecting the signal amount, and output to the body control unit 210 ofthe camera 1.

The readout unit 214 of the camera 1, by controlling the verticalcontrol unit 70, performs the first readout mode in which all pixel rowsare sequentially selected and signal of each pixel is readout, and thesecond readout mode in which signals from the AF pixel row and from theimaging pixel row are separately read out.

In a case the first readout mode has set by the readout unit 214, thevertical control unit 70 sequentially selecting pixel row and makes eachpixel output signal. In FIG. 15 , the vertical control unit 70sequentially selects the imaging pixel rows 401, 402, the AF pixel rows403 a, 404 a, 403 b, and 404 b from the 1st row toward the 16th row.Further, the vertical control unit 70 makes each pixel of the selectedimaging pixel row or AF pixel row output signal to the vertical signalline 60. The readout unit 214 reads out the signal output to thevertical signal line 60. An example of a signal readout method in thefirst readout mode will be described below.

First, the vertical control unit 70 turns to on state the selectionunits 56 of the R pixel 13 (1,1) through the G pixel 13 (1,8), which arethe pixels in the first imaging pixel row 401 of the 1st row. Further,the vertical control unit 70 makes the selection units 56 of pixels inthe rows other than the 1st row turn to off state. Thereby, each signalof the R pixel 13 (1,1) through the G pixel 13 (1,8) in the 1st row isoutput, via the selection unit 56, to each of the signal lines 60 a to60 h which are connected. The readout unit 214 reads out the signals ofthe R pixel 13 (1,1) through the G pixel 13 (1,8) having been output tothe vertical signal lines 60.

Next, the vertical control unit 70 turns to on state the selection units56 of the G pixel 13 (2,1) through the first AF pixel 11 a (2,8), whichare the pixels in the first AF pixel row 403 a of the 2nd row. Further,the vertical control unit 70 makes the selection units 56 of pixels inthe rows other than the 2nd row turn to off state. Thereby, each signalof the G pixel 13 (2,1) through the first AF pixel 11 a (2,8) in the 2ndrow is output to each of the signal lines 60 a to 60 h. The readout unit214 reads out the signals of the G pixel 13 (2,1) through the first AFpixel 11 a (2,8), in the 2nd row, having been output to the verticalsignal lines 60.

Similarly, the vertical control unit 70 selects the 3rd and subsequentpixel rows (the first imaging pixel row 401, the second imaging pixelrow 402, the first AF pixel row 403, the second AF pixel row 404) in theorder of the 3rd row, the 4th row, the 5th row, and the 6th row.Further, the vertical control unit 70 makes each pixel of the selectedimaging pixel row or AF pixel row output signal to the vertical signalline 60. The readout unit 214 reads out the signal output to thevertical signal line 60.

As described above, in the first readout mode, the readout unit 214reads out a signal from each pixel of all the pixel rows. The signalhaving read out from each pixel is output to the body control unit 210after being subjected to signal processing by the column circuit unit 80or the like.

In a case the second readout mode is set by the readout unit 214, thevertical control unit 70 separately performs of outputting of the signalof each pixel in the AF pixel row to the vertical signal lines 60 andoutputting of the signal of each pixel in the imaging pixel row to thevertical signal lines 60. In the present embodiment, the verticalcontrol unit 70 first sequentially selects only the AF pixel row and leteach pixel of the selected AF pixel row output a signal to the verticalsignal lines 60. Then, the vertical control unit 70 sequentially selectsthe imaging pixel row and let each pixel of the selected imaging pixelrow output a signal to the vertical signal lines 60. The readout unit214 first reads out only the signal output to the vertical signal lines60 from each pixel of the AF pixel row, and then reads out the signaloutput to the vertical signal lines 60 from each pixel of the imagingpixel row.

An example of a signal readout method in the second readout mode will bedescribed below. It is to be noted, the vertical control unit 70 selectsthe AF pixel row in which the AF pixel pair selected by the pixelselection unit 213 is arranged, in one (or a plurality of) focusdetection areas 100 set by the area setting unit 211. In the exampleshown below, it is assumed that the first AF pixel pair is selected bythe pixel selection unit 213 based on the exit pupil distance of thephotographing optical system 31.

First, the vertical control unit 70 turns to on state the selectionunits 56 of the G pixel 13 (2,1) through the first AF pixel 11 a (2,8)which constitute the first AF pixel row 403 a of the 2nd row shown inFIG. 15 . Further, the vertical control unit 70 makes the selectionunits 56 of pixels in the rows other than the 2nd row turn to off state.Thereby, each signal of the G pixel 13 (2,1) through the first AF pixel11 a (2,8) is output, via the selection unit 56, to each of the signallines 60 a to 60 h which are connected. The readout unit 214 reads outthe signals of the G pixel 13 (2,1) through the first AF pixel 11 a(2,8) having been output to the vertical signal lines 60.

Next, the vertical control unit 70 turns to on state the selection units56 of the G pixels 13 (6,1) through the second AF pixel 12 a (6,8) whichconstitute the second AF pixel row 404 a of the 6th row shown in FIG. 15. Further, the vertical control unit 70 makes the selection units 56 ofpixels in the rows other than the 6th row turn to off state. Thereby,each signal of the G pixel 13 (6,1) through the second AF pixel 12 a(6,8) is output to each of the signal lines 60 a to 60 h. The readoutunit 214 reads out the signals of the G pixel 13 (6,1) through thesecond AF pixel 12 a (6,8) in the 2nd row, having output to the verticalsignal lines 60.

Although not shown, a plurality of the first AF pixel rows 403 a and aplurality of the second AF pixel rows 404 a are also arranged in afterthe 16th row. The vertical control unit 70 sequentially selects only theplurality of the first AF pixel rows 403 a and the plurality of thesecond AF pixel row 404 a toward the column direction (+Y direction).The vertical control unit 70 causes each pixel of the selected first AFpixel row 403 a and the second AF pixel row 404 a to output a signal tothe vertical signal lines 60. The readout unit 214 reads out signalsoutput to the vertical signal line 60 from the G pixels 13, the first AFpixels 11 a, and the second AF pixels 12 a. The signals sequentiallyread from each AF pixel row are output to the body control unit 210after being subjected to signal processing by the column circuit unit 80or the like.

After reading out the signal from each pixel of the AF pixel row, thevertical control unit 70 sequentially selects the imaging pixel rowtoward the column direction (+Y direction). The vertical control unit 70causes each pixel of the selected imaging pixel row to output a signalto the vertical signal line 60. The readout unit 214 reads out signaloutput to the vertical signal line 60 from each pixel in the imagingpixel rows. The vertical control unit 70 turns to on state the selectionunits 56 of the R pixel 13 (1,1) through the G pixel 13 (1,8) which arein the first imaging pixel row 401 of the 1st row shown in FIG. 15 .Further, the vertical control unit 70 makes the selection units 56 ofpixels in the rows other than the 1st row turn to off state. Thereby,each signal of the R pixel 13 (1,1) through the G pixel 13 (1,8) isoutput to each of the signal lines 60 a to 60 h. The readout unit 214reads out the signals of the R pixel 13 (1,1) through the G pixel 13(1,8) having been output to the vertical signal lines 60.

Next, the vertical control unit 70 turns to on state the selection units56 of the R pixel 13 (3,1) through the G pixel 13 (3,8) which constitutethe first imaging pixel row 401 of the 3rd row shown in FIG. 15 .Further, the vertical control unit 70 makes the selection units 56 ofpixels in the rows other than the 3rd row turn to off state. Thereby,each signal of the R pixel 13 (3,1) through the G pixel 13 (3,8) isoutput to each of the signal lines 60 a to 60 h. The readout unit 214reads out the signals of the R pixel 13 (3,1) through the G pixel 13(3,8) having been output to the vertical signal lines 60.

Further, the vertical control unit 70 turns to on state the selectionunits 56 of the G pixel 13 (4,1) through the B pixel 13 (4,8) whichconstitute the first imaging pixel row 402 of the 4th row shown in FIG.15 . Further, the vertical control unit 70 makes the selection units 56of pixels in the rows other than the 4th row turn to off state. Thereby,each signal of the G pixel 13 (4,1) through the B pixel 13 (4,8) isoutput to each of the signal lines 60 a to 60 h. The readout unit 214reads out the signals of the G pixel 13 (4,1) through the B pixel 13(4,8) having been output to the vertical signal lines 60.

Similarly, with respect to the 5th row and subsequent rows, the verticalcontrol unit 70 sequentially selects the imaging pixel rows (firstimaging pixel row 401, second imaging pixel row 402). The verticalcontrol unit 70 makes each pixel of the selected the first imaging pixelrow 401 and the second imaging pixel row 402 output signal to thevertical signal line 60. The readout unit 214 reads the signals outputfrom the R pixel 13, the G pixel 13, and the B pixel 13 to the verticalsignal line 60. The signals sequentially read from each imaging pixelrow are output to the body control unit 210 after being subjected tosignal processing by the column circuit unit 80 or the like.

As described above, in the second readout mode, the readout unit 214controls the vertical control unit 70 to read out a signal from eachpixel in the AF pixel row prior to read out a signal from each pixel inthe imaging pixel row. Therefore, the first and second signals Sig1 andSig2 of the AF pixel pair can be read out at high speed, and the timerequired for focus adjustment can be shortened. Further, since thereading unit 214 reads out the signal of each pixel of the AF pixel rowand the signal of each pixel of the imaging pixel row separately, thesignal used for the focus detection can be efficiently obtained, and theload for processing signals for AF can be reduced. The camera 1according to the present embodiment reads out the first and secondsignals Sig1 and Sig2 of the AF pixel pair selected based on the exitpupil distance of the photographing optical system 31 and performs thefocus detection process. Thus, highly accurate focus detection can beperformed.

It is to be noted, in a case the second readout mode is set, the readoutunit 214 may read out a signal from each pixel of the imaging pixel rowprior to read out a signal from each pixel in the AF pixel row. Even insuch a case, since the signal of the AF pixel pair selected based on theexit pupil distance of the photographing optical system 31 is read outand the focus detection process is performed, the focus detection can beperformed with high accuracy. Further, since the readout unit 214 readsout the signal of each pixel of the AF pixel row and the signal of eachpixel of the imaging pixel row separately, the load for processingsignals for AF can be reduced.

Moreover, the readout unit 214, in a case reading out signals from eachpixel in the imaging pixel row (the first imaging pixel row 401, thesecond imaging pixel row 402) in the second readout mode, may read outsignals by performing thinning out readout in which pixels of specificrow or column are thinned. In a case performing the thinning outreading, the reading unit 214 selects imaging pixels in a specific rowor column among all the imaging pixels and reads out a signal from theselected imaging pixel. By controlling the vertical control unit 70,since the readout unit 214 skips reading the signal of the pixel of aspecific row or column, the signal can be read out at high speed. Inthis case, the signals from the AF pixel row can be read out beforereading out the signals from the imaging pixel row in the second readmode, and the signals from the imaging pixel row can be read out at highspeed. Therefore, in a case displaying a live view image or shooting amoving image, by performing in the second readout mode, it is possibleto perform high-speed focus detection and high-speed shooting. It is tobe noted, the readout unit 214 may read out signals from a plurality ofimaging pixels through adding the signals.

According to the above-described embodiment, the following effects canbe obtained.

(1) The focus detection device, comprises: the imaging unit (the imagesensor 22) having the first pixel and the second pixel (the AF pixels)each of which receives light transmitted through the optical system andoutputs signal used for focus detection, and the third pixel (theimaging pixel) which receives light transmitted through the opticalsystem and outputs signal used for image generation; the input unit (thebody control unit 210) to which the information regarding the opticalsystem is input; the selection unit (the image selection unit 213) thatselects at least one of the first pixel and the second pixel based onthe information input to the input unit; the readout unit (the readoutunit 214) that reads out the signal from at least one of the first pixeland the second pixel based on a selection result of the selection unitat a timing different from the timing of reading out the signal from thethird pixel to be read out; and the focus detection unit 215 thatperforms the focus detection based on at least one of the signals of thefirst pixel and the second pixel which read out by the readout unit. Inthe present embodiment, the readout unit 214 reads a signal from eachpixel in the AF pixel row prior to read out a signal from each pixel inthe imaging pixel row. Therefore, the focus detection device can readout the signals of the AF pixel pair at high speed, and can performfocus adjustment at high speed. Moreover, since the readout unit 214reads out the signal of each pixel of the AF pixel row and the signal ofeach pixel of the imaging pixel row separately, the load for processingsignals for AF can be reduced. Further, the focus detection unit 215performs the focus detection process using the signal output from the AFpixel pair selected based on the exit pupil distance of thephotographing optical system 31. Therefore, highly accurate focusdetection can be performed.

The following variations are also within the scope of the presentinvention, and one or more of the variations can be combined with theabove-described embodiment.

Variation 1

In the first embodiment, although three reference exit pupils (the firstto third exit pupils EP1 to EP3) were used as the reference exit pupils,it may be two reference exit pupils or four or more reference exitpupils.

Variation 2

The method of obtaining the exit pupil distance depending on the imageheight is not limited to the method of obtaining using theabove-mentioned formula (1). For example, instead of the formula (1), acalculation formula using the cube of the image height can be used.Further, information (table) showing the relationship between the imageheight and the exit pupil distance may also be used without using thecalculation formula.

Variation 3

In the first embodiment, an example in which information regarding theexit pupil distance is stored in advance in the lens memory 33 or thelike and the information regarding the exit pupil distance is input fromthe interchangeable lens 3 to the camera body 2 has been described.However, the information regarding the exit pupil distance may be inputto the camera body 2 from other than the interchangeable lens 3. Forexample, the body memory 23 may store the information regarding the exitpupil distance in advance, and the body control unit 210 may acquire theinformation regarding the exit pupil distance from the body memory 23.Further, the camera body 2 may acquire the information regarding theexit pupil distance from a storage medium or may acquire the informationregarding the exit pupil distance from an external device by wiredcommunication or wireless communication. It is to be noted, theinformation regarding the exit pupil distance may be informationregarding the exit pupil distance corresponding to one image height.

Variation 4

In the first embodiment, the parameters (h4) and (h2) and the constantterm Co, used for calculating the exit pupil distance Po (H) have beendescribed as examples of the information regarding the exit pupildistance. However, the camera body 2 may acquire the value Po (H) itselfof the exit pupil distance according to an image height, from theinterchangeable lens 3, the storage medium, or the like as theinformation regarding the exit pupil distance.

Variation 5

In the above-described embodiment, an example in which first to third AFpixel pairs having different deviation amounts are arranged on the imagesensor 22 as a plurality of types of AF pixel pairs has been described.However, a plurality of types of AF pixel pairs having differentarrangement positions of the light-shielding portions between the colorfilter 51 and the photoelectric conversion unit 42 may be arranged onthe image sensor 22. FIG. 16 is a diagram showing a configurationexample of a AF pixel of the image sensor 22 according to the presentvariation. In the figure, the same reference signs are assigned to thesame or corresponding parts as those in the above-described embodiment.

The light-shielding portion 43L of the first AF pixel 11 a is provided,between the color filter 51 and the photoelectric conversion unit 42,with a predetermined distance h1 from the photoelectric conversion unit42. The light-shielding portion 43L of the first AF pixel 11 b isprovided, between the color filter 51 and the photoelectric conversionunit 42, with a predetermined distance h2 from the photoelectricconversion unit 42. The light-shielding portion 43L of the first AFpixel 11 c is provided, between the color filter 51 and thephotoelectric conversion unit 42, with a predetermined distance h3 fromthe photoelectric conversion unit 42. The distance h2 is smaller thanthe distance h1 and larger than the distance h3. That is, h1>h2>h3. Asdescribed above, arranged positions of the light-shielding portions 43Lare different in the first AF pixels 11 a, 11 b, and 11 c to each other.Further, in the second AF pixels 12 a, 12 b, 12 c constituting each AFpixel pair, the arrangement positions of the light-shielding portions43R are different from each other. Thereby, the first to third AF pixelpairs can perform pupil division corresponding to different incidentangles, as in the case of the above-described embodiment.

Variation 6

In the first embodiment, an example in which one photoelectricconversion unit is arranged in one pixel has been described, however, aconfiguration in which two or more photoelectric conversion units areincluded per pixel may be adopted.

Variation 7

FIG. 17 is a diagram showing a configuration example of a AF pixel ofthe image sensor 22 according to the present variation. As an example,FIG. 17 shows a cross-sectional view of a part of three types of AFpixel pairs in the focus detection area 100 c shown in FIG. 2 . In thefigure, the same reference signs are assigned to the same orcorresponding parts as those in the above-described embodiment. Each ofthe three types of AF pixels shown in FIG. 17 (a) to FIG. 17 (c)includes a microlens 44, and a first and second photoelectric conversionunits 42 a and 42 b each of which photoelectrically convert the lighttransmitted through the microlens 44. In the present variation, thelight receiving areas, of a first photoelectric conversion units 42 aand a second photoelectric conversion unit 42 b are different from eachother in the first to third AF pixel pair. In this case as well, thefirst to third AF pixel pairs can perform pupil division correspondingto different incident angles, as in the case of the above-describedembodiment.

Variation 8

The pixel selection unit 213 may configure to select a plurality oftypes of AF pixel pairs. In this case, the focus detection unit 215 maycalculate a plurality of defocus amounts from selected plurality oftypes of AF pixel pairs, and the movement amount of the focusing lens 31b may be calculated based on the average value of the defocus amounts.For example, the moving amount of the focusing lens 31 b may bedetermined based on the average value of, the defocus amount calculatedusing the first and second signals Sig1 and Sig2 of the first AF pixelpair and the defocus amount calculated using the first and secondsignals Sig1 and Sig2 of the second AF pixel pair.

Variation 9

In the above-described embodiment, the case where the primary colorsystem (RGB) color filter is used for the image sensor 22 has beendescribed, but the complementary color system (CMY) color filter may beused.

Variation 10

The imaging device described in the above-described embodiment andvariations may be applied to a camera, a smartphone, a tablet, a camerabuilt in a PC, an in-vehicle camera, a camera mounted on an unmannedaerial vehicle (drone, radio-controlled model, etc.), etc.

Although various embodiments and variations have been described above,the present invention is not limited to these contents. Other aspectsconceivable within the scope of the technical idea of the presentinvention are also included within the scope of the present invention.

The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 2018-137274filed Jul. 20, 2018.

REFERENCE SIGNS LIST

1 Imaging Device, 2 Camera Body, 3 Interchangeable Lens, 11 AF pixel, 12AF pixel, 13 Imaging Pixel, 22 Image Sensor, 31 Photographing OpticalSystem, 32 Lens Control Unit, 42 Photoelectric Conversion Unit, 210 BodyControl Unit, 211 Area Setting Unit, 212 Distance Calculation Unit, 213Pixel Selection Unit, 214 Readout Unit, 215 Focus Detection Unit, 216Image Data Generation Unit.

The invention claimed is:
 1. An imaging device, comprising: a firstpixel and a second pixel each of which receives light transmittedthrough an optical system and outputs a signal used for focus detection;a third pixel which receives light transmitted through the opticalsystem and outputs a signal used for image generation; and a controlunit that comprises a processor and functions as a readout unit thatreads out the signal of the first pixel or the signal of the secondpixel, which is selected based on information regarding the opticalsystem, at a timing different from a timing of reading out the signalfrom the third pixel.
 2. The imaging device according to claim 1,wherein the readout unit reads out the signal of the first pixel or thesignal of the second pixel before reading out the signal of the thirdpixel.
 3. The imaging device according to claim 2, wherein the readoutunit can switch between (i) a first readout in which the signal of thefirst pixel or the signal of the second pixel is read out before readingout the signal of the third pixel and (ii) a second readout in which,following reading of the signal of the first pixel, reading of thesignal of the third pixel is performed and, following reading of thesignal of the third pixel, reading of the signal of the second pixel isperformed.
 4. The imaging device according to claim 3, comprising aplurality of the third pixels, wherein the readout unit performs thefirst readout (i) when the signals of a part of the plurality of thethird pixels are to be read out or (ii) when the signals of theplurality of the third pixels are to be added and read out, and thereadout unit performs the second readout when the signals of theplurality of the third pixels are to be read out.
 5. The imaging deviceaccording to claim 1, wherein: the third pixel is connected to at leastone of the first pixel and the second pixel, and a signal line isprovided in a first direction.
 6. The imaging device according to claim5, wherein the third pixel is provided between the first pixel and thesecond pixel in the first direction.
 7. The imaging device according toclaim 5, wherein: (i) a first pixel group in which a plurality of thefirst pixels are provided in a second direction intersecting the firstdirection and (ii) a second pixel group in which a plurality of thesecond pixels are provided in the second direction, are provided in thefirst direction; and the readout unit reads out signals of the firstpixel group or signals of the second pixel group selected based on theinformation.
 8. The imaging device according to claim 7, wherein: athird pixel group having a plurality of the third pixels in the seconddirection is provided between the first pixel group and the second pixelgroup; and the readout unit reads out the signals of the first pixelgroup or the signals of the second pixel group at a timing differentfrom the timing signals of the third pixel group are read out.
 9. Theimaging device according to claim 8, wherein: the readout unit reads outthe signals of the first pixel group or the signals of the second pixelgroup before reading out the signals of the third pixel group.
 10. Theimaging device according to claim 1, comprising a plurality of focusdetection areas each of which has the first pixel and the second pixel,wherein the readout unit reads out the signal of the first pixel or thesignal of the second pixel based on a position of the focus detectionarea and the information.
 11. The imaging device according to claim 10,wherein: the readout unit reads out the signals of the first pixels orthe signals of the second pixels in the plurality of focus detectionareas.
 12. The imaging device according to claim 10, wherein: when thefirst pixel at one focus detection area is selected, the readout unitreads out signals of the first pixels at other focus detection areas,and when the second pixel at one focus detection area is selected, thereadout unit reads out signals of the second pixels at other focusdetection areas.
 13. The imaging device according to claim 10, wherein:the readout unit reads out the signal of the first pixel or the signalof the second pixel based on the information and the position of thefocus detection area farthest from an optical axis among the pluralityof focus detection areas.
 14. The imaging device according to claim 13,wherein: when the first pixel at the focus detection area farthest fromthe optical axis among the plurality of focus detection areas isselected, the readout unit reads out signals of the first pixels atother focus detection areas; and when the second pixel at the focusdetection area farthest from the optical axis among the plurality offocus detection areas is selected, the readout unit reads out signals ofthe second pixels at other focus detection areas.
 15. The imaging deviceaccording to claim 10, wherein: each of the plurality of focus detectionareas has a first focus detection region and a second focus detectionregion that is farther from an optical axis than the first focusdetection region; and the readout unit reads out the signal of the firstpixel or the signal of the second pixel based on a position of thesecond focus detection region and the information.
 16. The imagingdevice according to claim 15, wherein: when the first pixel in thesecond focus detection region is selected, the readout unit reads outthe signal of the first pixel also in the first focus detection region,and when the second pixel in the second focus detection region isselected, the readout unit reads out the signal of the second pixel alsoin the first focus detection region.
 17. The imaging device according toclaim 10, wherein: the control unit also functions as a setting unitthat can set a focus detection area among the plurality of focusdetection areas; and the readout unit reads out the signal of the firstpixel or the signal of the second pixel based on the information and aposition of the focus detection area set by the setting unit.
 18. Theimaging device according to claim 1, wherein the information isinformation regarding an exit pupil distance of the optical system. 19.The imaging device according to claim 1, wherein the information isinformation regarding a position in an image plane and an exit pupildistance of the optical system.
 20. The imaging device according toclaim 1, comprising a plurality of the first pixels and a plurality ofthe second pixels, wherein: each of the plurality of the first pixelsincludes a pixel that receives light having passed through a first pupilregion of the optical system and a pixel that receives light havingpassed through a second pupil region, different from the first pupilregion, of the optical system; and each of the plurality of the secondpixels includes a pixel that receives light having passed through thefirst pupil region and a pixel that receives light having passed throughthe second pupil region.
 21. The imaging device according to claim 1,wherein: each of the first pixel and the second pixel has aphotoelectric converter; and an area of light receiving part of thephotoelectric converter of the first pixel that receives light isdifferent from an area of light receiving part the photoelectricconverter of the second pixel that receives light.
 22. The imagingdevice according to claim 1, comprising a generator that generates imagedata based on signals output from at least one of the first pixel, thesecond pixel, and the third pixel.
 23. An interchangeable lenscomprising: a detachable portion that enables to attach and detach tothe imaging device according to claim
 1. 24. An imaging apparatus,comprising: the imaging device according to claim 1, wherein the controlunit also functions as a focus detection unit that performs focusdetection based on the signal of the first pixel or the signal of thesecond pixel read out by the readout unit.
 25. A camera comprising theimaging device according to claim 1.